KYIV, - Ukrainian troops, said on Saturday they had taken the key stronghold of Lyman in occupied eastern Ukraine, a vicious defeat that prompted a close ally of President Vladimir Putin to call for the possible use of low-grade nuclear weapons.
The capture came just a day after Putin proclaimed the annexation of four Ukrainian regions - including Donetsk, where Lyman is located - and placed them under Russia's nuclear umbrella, at a ceremony that was condemned by Kyiv and the West as an illegitimate farce.

The collapse of another Russian front line was greeted by calls for nuclear strikes by some military bloggers and political figures in Russia, including the Chechen leader Ramzan Kadyrov, a close ally of Putin. “More drastic measures should be taken, up to the declaration of martial law in the border areas and the use of low-yield nuclear weapons,” Kadyrov wrote in a comment on his Telegram channel.

Putin has previously threatened to resort to nuclear weapons if Russia’s goals in Ukraine continue to be thwarted. The annexation brings the use of a nuclear weapon a step closer by giving Putin a potential justification on the grounds that “the territorial integrity of our country is threatened,” as he put it in his speech last week.

He renewed the threat on Friday with an ominous comment that the U.S. atomic bombing of Hiroshima and Nagasaki created a “precedent” for the use of nuclear weapons, echoing references he has made in the past to the U.S. invasion of Iraq as setting a precedent for Russia’s invasion of Ukraine.

U.S. and Western officials say they still think it unlikely that Putin will carry out his threats. Most probably, they say, he is hoping to deter the West from providing ever more sophisticated military assistance to Ukraine while the mobilization of an additional 300,000 troops allows Russia to reverse or at least halt its military setbacks on the battlefield.

However, U.S. and Europe are taking the threats seriously. White House national security adviser Jake Sullivan said on Sunday that there would be “catastrophic consequences” if Russia resorts to the use of nuclear weapons. He refused to specify what those would be but said the precise consequences had been spelled out privately to Russian officials “at very high levels.”